Ignition and control system for gas burners



Nov. 10, 1970 J. A. WRIGHT 3,539,283

l IGNITION AND CONTROL SYSTEM FOR GAS BURNERS Filed May 7, 1969 United States Patent O 3,539,283 IGNITION AND CONTROL SYSTEM FOR GAS BURNERS James A. Wright, Webster Groves, Mo., assignor to Emerson Electric Co., St. Louis, Mo., a corporation of Missouri Filed May 7, 1969, Ser. No. 822,577 Int. Cl. F23h 5/02 U.S. Cl. 431-78 8 Claims ABSTRACT OF THE DISCLOSURE A make-and-break spark igniter in which the breaker ar-m is a double throw and completes a circuit to open an electromagnetic fuel valve each time it breaks the ignition circuit to produce a spark.

'Ihis invention relates to control systems for the safe ignition and operation of gaseous fuel burners and particularly to safety means contingent upon operation of an igniter to supply fuel to the burner.

-An object of the invention isto provide a particularly simple and inexpensive system for the direct ignition of gaseous fuel burners which is safe and reliable in operation.

A further object is to provide an ignition and control system for gaseous fuel burners in which the movable element of a make-and-break-type spark igniter, upon moving in a direction to break the igniter circuit, completes a circuit for the energization of fuel supply means.

Further objects and advantages will appear from the following description when read in connection with the accompanying drawing.

The single iigure of the drawing is a schematic view of an ignition and control system for gas burners constructed in accordance with the invention.

Referring to the drawing,4 the primary elements of the system are: a gaseous fuel burner indicated at 10, a biased closed7 eelctromagnetically operated valve 12 in a fuel supply line 14, a spark igniter generally indicated at 16, a flame responsive switch generally indicated at 18, a space thermostat 20, a current limiting resistor 22, a fusible link 24, and a pair of power source terminals 26 and 28.

The flame responsive switch 1'8 comprises a rod 30 having a relatively low coeiiicient of thermal expansion and a tube 32 having a relatively high coefficient of thermal expansion. The tube 32 has a closed outer end to which one end of rod 30 is iixed and an inner open end which is suitably iixed to support means. The free end of rod 30 projects outward from the open end of tube 32 and carries thereon a contact bar 34 arranged to span a pair of stationary contacts 36 and 38.

The flame responsive switch 1 8 is disposed so that the flame of burner will impinge on the tube 32 or at least heat it rapidly. When the tube s at normal ambient temperature in the absence of flame at burner 10, it is in a contracted position which effects an extension of rod 30 and bridges or closes the contacts 36 and 3'8,

The spark igniter 16 includes a solenoid comprising a winding 40 and a plunger 42, a pair of spaced stationary contacts 44 and 46, and a resilient, pivoted, contact arm 48 biased into contact with stationary contact 44 by a spring 50. The lower end of plunger 42 engages the contact arm 48, and when the solenoid winding 40 is energized, the plunger 42 is caused to move downward suiiiciently to separate the contact arm from stationary contact 44 and move it into contact with stationary contact 46. The solenoid winding 40 is connected across power source terminals 26-28 through the thermostatic switch 20 and ice through the flame switch 1'8 by leads 52, 54, 56, '58, 60 and `62.

The biased closed, electromagnetic gas valve 12 includes a solenoid winding (not shown) which is connected across the power source terminals 26-28 through the thermostatic switch 20 and through the circuit limiting resistor 22 by the leads 52, 54, 64, and 62. The value of resistor 22 is such that it will permit a sufficient level of energization of the electromagnetic valve solenoid winding, at supply line voltage, to hold the valve in an open position against its bias once it has been lmoved from its closed to an open position, but it is also such that it limits the level of energization of the valve solenoid winding to a point below that which would eiiect an opening of the valve from its biased closed position.

Circuit connections paralleling resistor 22 are, however, provided which, when completed, permit an energization level of the valve solenoid winding which will cause the valve to be opened from its biased closed position. These connections include the stationary contact 46, the pivoted contact arm 48 of igniter 16, and leads 66 and 60.

OPERATION When the thermostatic switch 20 closes, the solenoid winding 40 of the igniter 16 will be energized, causing contact arm 46 to break from stationary contact 44 and to make with stationary contact 46, as shown in dotted line. The breaking of contact arm 48 from contact 44 produces a spark for ignition of fuel issuing from the ports of burner 10, and its making with contact 46 completes the low resistance path paralleling the resistor 22, Whereby the solenoid winding of electromagnetic valve 12 is energized to a level suiiicient to effect the opening of valve 12 and permit fuel to flow to burner 10.

When the contact arm 48 breaks with stationary contact 44, it also eifects de-energization of igniter solenoid winding 40 so that the contact arm 48 after being separated from contact 44 and being carried into engagement with contact 46 by momentum is returned again to its solid line position in engagement with stationary contact 44 by spring S0. The contact arm or breaker arm is therefore caused to oscillate at some frequency, depending inter alia upon the mass of the plunger 42 and arm 48, the flexibility of arm 48, and the strength of spring 50.

While the period of engagement of arm 4:8 with stationary contact 46 to effect the opening of valve 12 need only be a short period of time, this period may readily be eX- tended so as to provide a current pulse of longer duration by increasing the flexibility of contact arm 42 or by resiliently mounting the stationary contact 66.

Under conditions of normal operation, the sparking produced by the breaking of contact arm 48 with contact 44 will ignite the burner 10 in a matter of a few seconds. The burner Haine will then heat the tube 32 of llame responsive switch 18, causing it to expand and open the switch contacts 36 and 38 thereby de-energizing the winding 40 of the igniter solenoid and rendering the igniter 16 inoperative. When igniter 16 becomes inoperative, the arm 48 comes to rest biased against stationary contact 44 so that the current pulses which were intermittently energizing the winding of the electromagnetic valve sufiiciently to open the valve are now discontinued. The valve 12 remains open, however, inasmuch as suilicient current passes through resistor 22 to hold valve 12 open.

When the thermostat 20 is satisfied it will open, thereby completely de-energizing electromagnetic valve 12 and permitting it to return to its biased closed position.

If, during operation, the electrical power supply fails momentarily, permitting valve 12 to close, the valve will not again open upon resumption of a power supply until the flame responsive switch closes and the igniter is again operative to supply spark and current pulses to effect opening of the valve.

By requiring the separation of contact arm 48 from stationary contact 44 to complete-a circuit to effect the opening of the fuel valve 12, operation of the igniter prior to opening of the fuel valve is assured. If the contact arm 48 sticks, for any reason, in a position of engagement with contact 46, the fusible link 24 will fuse and completely de-energize valve 12. The fusible link 24 is calibrated to pass the current passing through resistor 22 and the intermittent current pulses across the contact 46 and contact arm 48, but it will not carry the continuous current which would flow through the contact arm 48 if it remains closed on Contact 46. Any other suitable, current-overload, circuit breaker may be used in lieu of the fusible link 24, such as, for example, a recycling, bimetal-type circuit breaker.

I claim:

1. In a control system for fluid fuel burners, a burner,

a biased closed electromagnetic fuel valve controlling the supply of fuel to said burner, a spark igniter comprising a stationary contacting element and a movable contacting element, a second stationary contacting element spaced from said rst-mentioned contacting element, electrically operated means operative to effect the cyclic movement of said movable contacting element alternately into engagement with said spaced stationary contacting elements and to alternately break engagement therewith, a source of electrical power, a Valve energizing circuit connecting said electromagnetic valve across said power source and including a series impedance element between said valve and one side of said power source operative to limit the energization level of said electromagnetic valve to a value which will hold the valve open once it is opened but is insufficient to effect opening of the valve from its biased closed position, circuit connections co-nnecting said firstmentioned stationary contacting element to the other side of said power source, circuit connections connecting said movable contacting element to the said one side of said power source, and circuit connections connecting said second stationary contacting element to said valve energizing circuit at a point between said electromagnetic valve and said impedance element, thereby to shunt said impedance element when said movable contacting element is in engagement with said second stationary contacting element and permit momentary sufficient energization of said electromagnetic valve to effect its opening, and said power source being sufficient to draw an ignition arc when said movable contact breaks with said first-mentioned contacting element.

2. In an ignition and control system for uid fuel burners, a source of electrical power, a biased closed electromagnetic valve controlling the supply of fuel to a burner, a spark igniter comprising a stationary contact and a movable contact, circuit connections connecting said stationary Contact to one side of said power source and said movable contact to the other side thereof, a valve circuit connecting said electromagnetic valve across said power source including a series impedance element between said valve and the said other side of said power source operative to limit the energization level of said electromagnetic valve to a value which is sucient to hold the valve open once it is open but which is insufficient to open the valve from its biased closed position, a second stationary contactspacedfrom said first-mentioned stationary contact, electrically operated means operative to oscillate said movable contact to alternately contact and break with said spaced stationary contacts, circuit connections connecting said second stationary contact with said valvecircuit at a point between said electromagnetic valve and said irnpedance element, thereby to shunt said impedance element when said movable contact is in engagement with said second stationary contacting element and thereby provide sufficient momentary energization of saidlelectromagnetic valve to effect its opening,vand said power source being sufficient to draw an ignition arc when said movable co'- tact breaks with said first-mentioned contact.

3. An ignition and control system as set forth in claim 1 which further includes a current responsive circuit breaker in saidelectromagnetic valve circuit responsive to a continuous full current flow therethrough to break the electromagnetic valve circuit, which continuous full flow of current would occur if said movable contact sticks in engagement with said second stationary contact.

4. An ignition and control system as set forth in claim 1 in which said movable contacting element is biased into contact with said first-mentioned stationary contacting element and in which a normally closed, fiame responsive switch responsive to burner flame to de-energize said electrically operated means is included in said circuit connections connecting said first-mentioned stationary contacting element to said other side of lsaid power source.

S. An ignition and control system for fluid fuel burners as set forth in claim 2 which further includes an inductance element in said circuit connections connecting said first-mentioned stationary contact to one side of said power source and said movable Contact to the other side thereof.

6. An ignition and control system for fluid fuel burners as set forth in claim 2 in which said electrically operated means operative to oscillate said movable contact is an electromagnet having a winding in series with said movable contact and said first-mentioned stationary contact.

7. An ignition andcontrol system as set forth in claim 2 in which said movable contacting element is a pivoted resilient arm, and in which said electrically operated means is operative to flex said arm when it is moved thereby into engagement with said second stationary contacting element thereby to prolong the engagement.

8. An ignition and control system as set fourth in claim 2 `in which said second stationary contacting element is resiliently supported and is moved slightly when engaged by said movable contact thereby to prolong the engagement.

References Cited UNITED STATES PATENTS 2,594,059 4/1952 Nagel 431-78 3,171,469v 3/1965 Mudd 431-78 3,323,019 5/1967 Takahashi 317--93 3,33 6,505 8/1967 Liesse 431-257 3,424,950 1/ 1969 Halm 317-93 EDWARD G. FAVORS, Primary Examiner U.S. Cl. X.R. 

